Impregnated felt



i i Y 1 continuous sheet on Fourdrinier Patented Sept. v 27, i938 Pierre DrewsemSandusky,

Barrett Company, New York,

tion of New Jersey.

NofDrawing. Original application February 4, h now Patent No..

is application No- 1926, Serial No.

86,098, 2,029,310. Divided and th vemb'er 16, 1935, Serial No.

2 (ci. se -m1 This invention relates to felt and more'par ticularly to felt adapted to be saturated with waterproofing compounds such as asphalt, coal tar, coal tar pitch or other bituminous waterproofing material, to form waterproof products for building, flooring, roofing and like purposes.

\ Heretofore the manufacture of felt intended to be saturated with Waterproofing compounds, such as liquid bituminous materials has usually been accomplished by employing one or following as raw materials:

(1) Rags which contain substantially a mix-i ture of cotton and wool;

(2) Rags consisting substantially of cotton;

(3) Rags which contain jute fiber in-the form of waste bagging;

(4) Rags which contain old carpets composed largely of jute with quantities of cotton and wool;

(5) Rags which contain rag clippings of all grades with varying amounts of paper; and

(6) Paper stock composed largely of waste paper.

These materials are partiallydisintegrated in rag cutters and thereafter,.while in suspension in water, are beaten in paper mill beaters, then jordaned if desired and finally formed into a or cylinder paper-making machines.

Rags are a relatively expensive raw material and the use of substantial proportions of the same in the manufacture of felt results in a relatively expensive product.

Paper stock composed largely of waste paper is a less expensive raw material than rags, but the use of large quantities of this material in the manufacture of felt tends to harden or stiffen the felt sheets and produce a product of inferior quality for many purposes.

Wood fibers have been recognized as a low cost material and proposals have been made tosubstitute such fibers for a portion of the more v expensive fibers hereinabove mentioned.

One object of this invention is to produce a low cost felt, of relatively great strength and having a relatively high capacity for absorbing waterproofing compounds, consisting substantially entirely of wood fibers. A further object of the invention is the production of felt by blending wood fibers whose principal function is to impart strength to the felt with other wood fibers of a character to impart a high capacity for absorption to form a felt having the desired strength and absorptive capacity. I

Other objects and advantages'of my invention more of the will appear from the tion.

oilio, assignor to The N. Y., a corporafollowing detailed descrip In accordance with this invention, wood fibers of relatively great strength are blended with other 1 wood fibers of relatively open structure and hav 5 ing high absorptive capacity in suitable proportions to produce a felt having the desired strength, 1

and bsorptive capacity. I

.As fibers in which strength is the predominant mamteristm- I may m oy unbleached's'ulfite 10 pu por kraft pu1p I resulting from the subjection sulfite process be employed in an unbleached condition since such greater strength than 1 The preparation-of sulfite pulpis a process well known in the art. 'It is preferred that the fibers ofwood to the" fibers possess relatively bleached fibers. Drastic or. over bleaching. particularly with strong bleaching agents avoided in case a for the reason that such; as chlorine,; shouldbe felt of high strength is desired such bleaching weakens the fibers and hence would result in an inferior felt as compared with a felt containing unbleached fibers or fibers which have been subjected to only a mild bleaching operation.

As strength fibers, the sulfite pulp may be partly or wholly replaced erally in the by. wood fibers known genpaper making artjas kraft (including waste kraft pulp).

Since the preparation of beta sulfite sti end kraft pulp is well known in art, and thes able, further the paper: making e materials are commercially availdescriptlon of the processes for the preparation thereof is believed to be unnecessary.

Of the two classes of wood fibers, those to be employed principally for imparting high absorptive capacity to the felt may be prepared by cooking wood substances in an alkaline medium and disintegrating the fibers by mechanical treatment, for example, ners or in beating engines or Jordan, engines.

by treatment withedge run- As an example of the preparation of absorptive fibers,

having a str weight. operation at have found that fibers having a high absorptive capacity may be or shavings It is preferred to perform the cooking wood substances such as spruce or hemlock may be tures in the presence of a solution of caustic soda treated at elevated temperaength of ten per cent or higher by temperatures of over C. and I prepared by cooking spruce'chips in the presence of a solution of to C. andsubsequently I fibers and disintegrating them in a beatingengine. In lieu of caustic soda solution,

a solution of other alkali may be employed as the cooking medium; It will be understood to those skilled in the art that the time for which the wood fibersare subjected to cooking or beating as hereinabove described, will depend on many factors among which may be mentioned the temperature of the solution to which the fibers are subjected, the strength of the solution, the amount of the charge, etc., and that the treatment of the fibers is carried out until the fibers are disintegrated and rendered absorbent to the desired extent which may be determined by inspecting and testing the fibers in the cooking or beating engine as the case may be.

Absorptive fibers may also be formed by cooking wood substances, such as spruce or hemlock chips or shavings in a calcium pentasulfide solution as described in U..S. Patent No. 996,225 of June 27, 1911 to Viggoj Drewsen, after which the fibers are disintegrated by treatment with edge runners or in the ordinary form of beating engine or Jordan engine. Instead of a solution of calcium pentasulfide, polysulfides of certain other alkali or alkaline earth materials, such as sodium pentasulfide, may be employed as the cooking medium.

.Having produced the pulp containing fibers of relatively high strength and pulp containing fibers to be employed for imparting high absorptive capacity to the felt, the two types of fibers are blended in proportions of from per cent to 45 per cent of strength fibers with from 55 per cent to 85 per cent of absorptive fibers and the resulting blend of fibers is formed into a felt sheet on Fourdrinier or cylinder felt-making machines. The percentages of the two types of fibers may be varied within the limits stated depending-upon the type of I felt desired tobe produced. For example, for a felt of exceptionally great strength and in which it is not important that a large amount of saturant be absorbed, the proportion of strength fibers may be increased'with a corresponding decrease in the proportion of absorptive fibers. On the other hand; if it is desired to produce a felt having relatively high saturatmg capacity, for example a felt capable of absorbing 150-170 per cent or more, e. g., more than 200 per cent by weight of bitumen, such as asphalt, the proportion of absorptive fibers may be increased with a corresponding decrease in the proportion of strength fibers. For example,

one felt suitable for manufacturing mineral surfaced roofing may consist of about percent of strength fibers and about 75 per cent of absorptive fibers. Such a felt having a thickness of 0.057 inch will have a tensile strength of 27 be produced more cheaply than the usual felt products containing substantial percentages of relatively expensive fibers such as rag fibers. My felt isadmirably adapted for employment as a fibrous base for water-proofed materials to be employed for building purposes such, for example, as siding and roofing.

This application is a division of my copending application Serial No. 86,098, filed February 4,

1926 which has issued as Patent No. 2,029,310, February 4, 1936.

It is to be understood that the above descriptionis to be interpreted as illustrative and' not in a limiting sense and that this invention is not restricted to the present disclosure otherwise than as defined by the appended claims.

I claim:

1. A flexible felt sheet consisting substantially entirely of wood fibers, said felt containing from 15 per cent to 45 per cent of fibers of relatively great strength from the group consisting of sulfite pulp and kraft pulp and from 55 per cent,

to 85 per cent of fibers having high absorptive capacity produced by cooking wood with a reagent of the group consisting of caustic alkali and alkaline sulfides, said felt being impregnated with waterproofing material.

2. A flexible felt sheet consisting substantially entirely of wood fibers, said felt containing from 15 per cent to 45 per cent of fibers of relatively great strength from. the group consisting of sulfite pulp and knit pulp and from 55 per cent to 85 per cent of fibers having high absorptive capacity produced by cooking wood with a re-' agent from the group consisting of caustic soda and polysulfides of alkali and alkali earth metals,

said felt being impregnated with bituminous waterproofing material. v

' PIERRE DREWSEN. 

